Question

I’m trying to set an Array only if it doesn’t exist but I cannot figure out how to do it since I get an error saying it doesn’t exist:

if (null == arr) { // arr cannot be resolved to a variable
    arr = new ArrayList<task>();
}

Isn’t there something such as isset() from php? Also what does <> hold?

Answer 1

No, you can not. Java is the language with strong static typing. There isn’t any isset like in JS.

The only way is to declare your variable arr before and assign null value to it.